I have the same problem, I used to be able to last one day on a charge, now my phone is down to 42% after three hours. I've used it my usual way, checking Facebook and e-mail in the morning and reading a book while listening to Spotify for my 1-hour commute to work. This usually brought the phone to 80-90% charge. I've activated iCloud sync for everything but backup, if that might matter.
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LizzanOct 14 '11 at 6:15

1

My question was closed as a duplicate, so I'll add the list of things I've tried that haven't worked: disable wifi, disable location for weather app, disable bluetooth, disable location for time zone setting. At this point it looks like a true bug, equivalent to the initial release of ios4 running on the 3G.
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Adrian CoxOct 14 '11 at 9:28

My battery is draining as well since the upgrade to iOS 5 - literally in a matter of hours instead of days. I see that most of the answers deal with general problems with short battery life on the iPhone. This is an iOS 5-specific problem; I'm having it too, and I've never had a problem with my battery before the upgrade. The problem is either with the OS itself, or with some service that has been enabled with the upgrade. The standard services to check (bluetooth, location services, etc) are helpful general reminders, but do not address this specific problem with iOS 5.
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user12014Oct 14 '11 at 13:01

14 Answers
14

I think I've found the answer for my case. Location services were completely innocent, and I've returned them to default settings. My phone synchronises with a Zimbra server, set up as an Exchange account. The update enabled sync of Reminders, but the Reminder sync didn't work. Removing Reminder sync from the Exchange account setup has stopped the battery level dropping while I watch.

My general advice is to check your mail accounts to see if anything new is being synchronised, and then disable it if you're not using it.

Just a quick test so far, but after disabling the Reminders sync with my work Exchange server, my phone has also cooled down and kept a 50% charge for 15 minutes now. I've also re-enabled most of what I disabled in @appe's answer. Hope it keeps up!
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LizzanOct 14 '11 at 13:22

+1: When I was on the betas I noticed syncing back to Google Exchange killed my battery life (70% to 0% in under 6 hours whilst sleeping), seems fine with it disabled though.
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Nicholas SmithOct 14 '11 at 15:20

Yes, this definitely worked for me too, thanks very much!
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LizzanOct 14 '11 at 15:43

I have a Google Apps account on my phone, but even though it shows a "Reminders" under the account name in the accounts list, there's no such option in the account details (so I can't disable it). Any tips?
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Rodrigo SieiroOct 15 '11 at 4:03

I've added a screenshot showing where the control is on my phone. What do you have in the red outlined section?
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Adrian CoxOct 15 '11 at 6:24

Tried turning off everything in 1 (not the apps, but I haven't run any using location services) and 3, unused stuff in 2, and my iPhone has still drained to 51% in 3 hours of basically sitting on my desk.
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LizzanOct 14 '11 at 12:50

After upgrading to iOS 5 I noticed a huge battery loss compared to normal (10% per hour) and my iPhone was regularly warm to the touch. The steps that resolved this issue for me were resetting all network settings (this restarted the iPhone) and then erasing all email accounts, including iCloud, and manually re-adding them.

After performing these steps my phone immediately cooled off and the battery was stable once again. Your mileage may vary.

This was certainly the solution for me for drain whilst "sleeping". I'm still getting visible drain when the screen is active though and am about 10-15% short at the end of the day than I'd expect/
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Dan KellyOct 28 '11 at 8:44

The question has been mostly covered, but I'll also point out that iOS5 will eat your battery a bit more than previous versions, there's plenty going on in the background with the iCloud sync, Photostream et al.

The ones that haven't been touched on that really helped my battery life over the betas are these:
1) Find my iPhone occasionally will ping and not fully shutdown location services and take a bit more running.
2) Heavy heavy games and apps won't always dump out of memory, this is mostly sorted now (mostly), and can cause a bit of a battery eating situation. If you've been playing a game and your phone is still warm manually kill it.
3)Photostream seems to run quite a lot, disable it if you don't really need it. Your photos still get backed up to iCloud.
4) Disable the weather and stock widgets

Those helped me get it back from half a day if I was lucky to a full day. There's a few that are a bit killing a chicken to appease the gods (looking at you number 4), but still worth ticking off if you want max battery life.

As for the technical why of iOS5 draining your battery much faster than the previous OS, this Fastmail blog article might give some specific clues (Fastmail is an email provider, and the issue described applies to the IMAP email protocol, but it might be hinting about a more general change in iOS):

Unfortunately, there’s a new and recent problem that has now appeared.

iOS 5 now uses long lived persistent IMAP connections (apparently
previous versions only used short lived connections). The problem is
that our ping packets every 4 minutes mean that the device
(iPhone/iPad/iPod) is "woken up" every 4 minutes as well. This means
the device never goes into a deeper sleep mode, which causes
significantly more battery drain when you setup a connection to the
Fastmail IMAP server on iOS 5 devices.

Given the rapid increase in use of mobile devices like iPhones, and
the big difference in battery life it can apparently cause, this is a
significant issue.

Look in Settings > Location Services to see what is using it all the time. I set up a Reminder to be triggered by arriving at a certain location. We'll see if that eats up my battery life!
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GEdgarOct 14 '11 at 20:32

Neither of us changed our use, and then both used to last all day. So something in the update has dramatically affected her battery life. I'll look into the location services, but we both have them on all the time with the new update.
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Jaydles♦Oct 14 '11 at 3:23

Mine is draining the battery faster too, but I think it is due to location services. I usually have no location app running, but I've been trying the new Reminders app with the "at location" option and that implies keeping the location service active all the time.

On the other hand, with iOS 4 my iPhone could handle 1-2 hours with the location service active, and now it works for almost 8 hours.

For me, disabling iTunes WiFi sync seemed to do the trick. Before, other methods like disabling location services and Ping, removing mail settings, etc. did not make any difference before - the battery would go from 100% charged to dead within 3-4 hours.

I have fixed a lot of iPhone batter problems in my day, and people who think they might even have a hardware problem find if they restore the device as new and sync the data back, they generally notice a large improvement in battery life. This is especially noticeable in upgrades of the operating system.

Obviously this is just hearsay, but I have heard it and said it a good thousand times.